Electric furnaces comprising graphite electrodes which introduce the electric energy by the formation of an electric arc (such as is known e.g. from DE-A-32 41 987 and DE-C-29 44 269) exhibit a relatively high electrode consumption at the tip, primarily if operated as an anode, which electrode consumption depends on the square of the current and is caused thermally by the electron exchange. So far, this electrode tip consumption had to be taken as a fact and has constituted a cost factor hitherto viewed as unavoidable.
The invention aims at avoiding these disadvantages and difficulties and has as its object to provide a method as well as an electric arc furnace for carrying out the method, by which the electrode consumption is substantially reduced. In particular, it shall also be possible to greatly reduce the consumption of a graphite electrode connected as an anode, such that the consumption of the anodically connected graphite electrode is not substantially higher than the consumption of a cathodically connected graphite electrode. However, this shall not be disadvantageous to the melting procedure, i.e. the efficiency and the melting capacity shall be at least equal to those of conventional electric arc furnaces.
According to the invention, this object is achieved in that organic substances are introduced into the electric arc via a central longitudinal recess of the graphite electrode.
The introduction of the organic substances into the hottest region of the electric arc furnace causes a decomposition of these substances, i.e. an energy-consuming splitting reaction. This leads to a cooling effect lowering the temperature at the electrode tip so much that the graphite consumption is considerably reduced.
Hollow electrodes have, e.g., been known from DE-A-29 00 864 and DE-A-30 22 566. According to DE-A-29 00 864 these known hollow electrodes serve for introducing lime, carbon, aluminum oxide or other alloying additives by means of a carrier gas, such as a noble gas, nitrogen, oxygen or air, or, according to DE-A-30 22 566, for introducing additives, such as silt, coke or lime.